This invention relates to rotating machines and in particular, to erosion resistant labyrinth seals for use in rotating machines.
As is well known in the art, labyrinth seals of the type generally employed in rotating machines, such as turbines, power expanders, compressors, pumps and the like, are highly susceptible to erosion. This is particularly true where the machine is processing dirty gases that contain a relatively high percentage of solids or other contaminants. A labyrinth seal, as the name implies, contains a series of labyrinth-like cavities which function to entrap a working fluid between a moving component of the machine and a stationary component. The fluid thus creates a barrier that isolates a high pressure region within the machine from a region of lower pressure.
Under the influence of the rotating machine component, the working fluid in the seal cavity is rotated at relatively high speed and any solids entrained in the fluid is hurdled by centrifugal force against the exposed surfaces of the seal. This along with the high operating temperature experienced by the seal and the corrosive effect of many working fluids leads to rapid erosion of exposed seal surfaces and early seal failure. Accordingly, seals of this type must be replaced often. Labyrinth seals, because of the very nature the job must perform, are generally positioned about the rotor assembly deep within the machine. To replace the seal the entire machine generally must be dismantled and rebuilt. This, of course, is a time consuming and costly procedure.